JPH0832011B2 - Television signal digital VTR - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to digital VTRs for television signals.

Configuration of Conventional Example and Problems Thereof In general, if a television signal is digitized and the digital signal is directly recorded in a recording device, the recording rate becomes about 100 Mbps, which is extremely high. V
In TR, if the digital signal is recorded as it is, the capacity of the recording tape becomes a problem.

Therefore, it is considered that the digital signal to be recorded is band-compressed to reduce the recording rate to about 1/2 while maintaining the input image quality before recording.

As a conventional image compression recording, there is one as described in JP-A-55-93539. FIG. 4 shows a conventional image compression recording device. In FIG. 4, reference numeral 51 is a compressed code block digital signal, 52 is a D / A converter, 53 is a digital signal to be recorded, and 54 is an optical read / write head. 55 is an analog signal read by the head 54, 56 is an A / D converter, 57 is an A / D converter 56
Is a digital signal converted by, 58 is a compressed DS signal that expands the recorded signal and corrects any error DS
P and 59 are digital image signals as the final output, 60 is a monitor for reproducing an image, and 61 is a disk-shaped recording medium.

The operation of the conventional image compression recording / reproducing apparatus configured as described above will be described.

In the case of the write operation, the compressed code block digital signal 51 is D / A converted and recorded on the disk-shaped recording medium 61 by the optical head 54. In the case of the reading operation, the analog signal read by the optical head 54 is A / D converted, and the signal compressed by the DSP 58 is expanded and monitored.

However, VT is used to compress and record such images.
If it is to be realized by R, since the recording medium is tape-shaped, its strength is lower than that of a disk-shaped medium and deformation occurs, so that the error rate becomes very large.

Further, in the field of VTR, if an image is compressed and recorded, the image quality is inevitably deteriorated. Especially in professional VTRs used in broadcasting stations and studios, it was common knowledge to record images without compression.

However, in order to popularize this for consumer use, it is indispensable to use the recording tape economically, and for that purpose, it is necessary to make the recording density high, and accordingly, the error rate at the time of recording and reproducing on the tape. Will increase.

In view of such a point, the present invention provides a digital VTR of a television signal that can correct only a minimum necessary block at the time of correction even if an error is detected when performing compression recording / reproduction of an image in the VTR. The purpose is to provide.

The television signal digital VTR of the present invention comprises a signal quantizing means for sampling an input television signal at a predetermined frequency and quantizing each sample into N bits, and a block for every L adjacent blocks of the sample. Block coding means for performing high-efficiency block coding on each block to reduce the number of bits to M bits (M ≦ N) per sample, and P bits for the data with the reduced number of bits. An error detection block is configured for each of the error detection blocks, and an error detection unit for performing error detection in the error detection block unit and an error correction unit for performing error correction for each of the error detection blocks are provided. To P = S ・ M ・ L (where S
Is an integer of 2 or more).

Description of Embodiments FIG. 1 is a schematic block diagram of a recording / reproducing system of a digital VTR when Hadamard transform is used as a high-efficiency coding method.

In FIG. 1, an analog TV signal input from the input terminal 101 (NTSC color TV signal is considered as an example) is A / D.
In the converter 102, for example, 4 fsc (fsc is a color subcarrier frequency) is sampled (8 bits), quantized, and then input to the next high efficiency encoder 103. This high-efficiency encoder 103 includes a blocker 104, a Hadamard converter 105,
And a quantizer 106, which reduces the number of bits to about 4 bits per sample while maintaining the image quality of the input signal. That is, originally, the bit rate of 114 Mbps is reduced to half, 57 Mbps, and high efficiency coding is performed. Then, in the next error correction encoder 107, a parity bit for detecting and correcting a bit error during reproduction is added, and finally recorded on the tape 109 via the recording head 108.
During reproduction, the output signal extracted from the reproduction head 110 is first checked by the error detector 111 whether a bit error has occurred during reproduction, and an error that can be corrected by the error correction decoder 112 based on the information. Is corrected by the parity added at the time of recording.

Then, the high-efficiency decoder 113 records the high-efficiency decoder 103
The inverse conversion is performed, and the original signal of 8 bits per sample is restored. That is, this high-efficiency decoder 113 includes an inverse quantizer 114, a Hadamard inverse transformer 115, and an inverse blocker 11
It consists of 6 blocks. Then, when an error exceeding the correction capability of the error correction decoder 112 occurs, the error modifier 117 approximately synthesizes a signal from adjacent samples of the sample in which the error occurred and replaces it with the error sample. To do. Finally, the D / A converter 118 restores the original analog TV signal and outputs it from the output terminal 119.

Now, the Hadamard transform is adjacent 21 (1: positive integer)
This is a block code in which the conversion is performed in block units with each sample as one block. Therefore, this block is called a Hadamard transform block. On the other hand, as described above, the recording data is constructed so that a bit error therein can be detected for each block of a certain fixed size, and this block is called an error detection block. If the size (the number of bits) of this error detection block is not in an integral multiple of the size (the number of bits) of the Hadamard transformed block after the above conversion, the following inconvenience occurs. As an example, consider a two-dimensional 8th order Hadamard transform, and consider a Hadamard transform block as shown in FIG. Where x1 ~
x8 corresponds to each sample point.

That is, the input column vector to the Hadamard transformer is X,
Let Y be the output column vector after Hadamard transformation Then, the function of the following equation is established between the two Y = H8 · X (2) where H8 is the Hadamard transformation matrix of 8th order and is given by the following equation. Here, "+" represents +1 and "-" represents -1.

Now, assuming that the Hadamard transform can reduce the number of bits from 8 bits to 4 bits per sample, the size of the Hadamard transform block after conversion is 4 bits × 8 =
It will be 32 bits. On the other hand, the size of the error detection block is
Assuming that, for example, 50 bits are set irrespective of the size of the Hadamard transform block, if an error is detected in the error detection block EB2 shown by the slanted line in FIG. 2, all the Hadamard transform blocks HB2, HB3, HB4 are May occur. Therefore, if the error is an uncorrectable error, the correction operation starts. In that case, the Hadamard transform blocks that must be replaced are HB2, HB3, HB4, and three blocks. The number of bits is equivalent to 96 bits. That is, if there is no relationship between the size of the Hadamard transform block and the size of the error detection block, even a region that is considerably wider than the region that should be originally replaced must be replaced. This is a major drawback in view of the fact that it is preferable in terms of image quality that error correction is limited to the smallest possible range.

In this embodiment, the input television signal is quantized into N bits, L adjacent samples are blocked, and Hadamard transform is performed to reduce the bits to M bits per sample. That is, the Hadamard transform reduces L × N bits per block to L × M bits.

Then, if the size of the block for error detection is P bits, the relation of P = S × M × L (4) is established (S: positive integer).

The situation when S = 2 is shown in FIG. In FIG. 3, the size of the error detection block is P = 64 bits. Now, when an error is detected in the error detection block EB2 with diagonal lines, the Hadamard transform blocks to be replaced by error correction are 2 blocks of HB3 and HB4, and the area to be replaced is equivalent to 64 bits. It can be seen that the number of bits in a block matches the minimum number of block replacements required.

Although the error modifier is placed after the high-efficiency decoder in the description of the embodiment of the present invention, this position may of course be placed before the high-efficiency decoder. Further, as a high-efficiency block coding method, it goes without saying that the present invention is also effective for block coding such as orthogonal transform coding other than Hadamard transform or vector quantization.

EFFECTS OF THE INVENTION In general, pixels replaced by error correction do not always have high correlation, and depending on the TV screen, the replacement portion may cause a large deterioration in image quality. Therefore,
The smaller the unit replaced by this error correction, the better.
According to the present invention, the replacement block is limited to the required minimum size, and even if image quality deterioration occurs due to replacement, the area can be minimized. Moreover, the recording rate is halved while maintaining the input image quality without increasing the error rate.
It can be reduced to a certain degree and recorded.

[Brief description of drawings]

Figure 1 shows a digital VTR using high-efficiency coding.
2 is a block diagram showing the outline of the configuration of FIG. 2, and FIG. 2 is a diagram showing the relationship between the error detection block and the Hadamard transform block that needs modification when the size relationship between the Hadamard transform block and the error detection block is not an integral multiple. FIG. 3 shows the relationship between the error detection block and the Hadamard transform block requiring the integer multiple when the size relationship between the Hadamard transform block and the error detection block is an integral multiple in one embodiment of the present invention. FIG. 4 and FIG. 4 are views showing a conventional image compression recording apparatus. 104 …… Blocker, 105 …… Hadamard transformer, 106
... Quantizer, 107 ... error correction encoder, 111 ... error detector, 112 ... error correction decoder, 114 ... dequantizer, 11
5 …… Hadamard inverse transformer, 116 …… Inverse blocker, 11
7 ... Error modifier, 51 ... Compressed code block digital signal, 52 ... D / A converter, 53 ... Digital signal to be recorded, 54 ... Optical enrichment / writing head, 55
…… Read analog signal, 56 …… A / D converter, 57…
… A / D converted digital signal, 58 …… DSP, 59 …… digital image signal, 60 …… monitor, 61 …… disc-shaped recording medium

 ─────────────────────────────────────────────────── --Continued from the front page Judgment panel for referee Judge Seiji Murai Judge Joji Tanabe Judge Keiichi Hashimoto (56) Reference JP 59-61244 (JP, A) JP 56-65316 (JP, JP, A) JP-A-55-93539 (JP, A) JP-A-58-45614 (JP, A)

Claims (1)

[Claims] 1. A signal quantizing means for sampling an input television signal at a predetermined frequency and quantizing each sample into N bits, and dividing the sample into adjacent L blocks. On the other hand, block coding means for performing high-efficiency block coding to reduce the number of bits per sample to M bits (M ≦ N) and error detection blocks for each P bits of the data with the reduced number of bits are formed. , Error detecting means for detecting an error in units of the error detecting blocks, and error correcting means for correcting an error in each of the error detecting blocks, and P = S.
A digital VTR for television signals, characterized in that the relationship of M and L (where S is an integer of 2 or more) is established.